Moulded ophthalmic article

ABSTRACT

The invention relates to moulded ophthalmic articles, especially contact lenses, which are obtainable by cross-linking a prepolymer which is the copolymerization product of (a) at least one polyalkylene glycol of the formula (1): HO--(CH 2  --CH 2  --O) n  --(CHY 1  --CHY 2  --O) m  --(CHY 3  --CHY 4  --O) p  --H or (1&#39;): HO--[(CH 2  --CH 2  --CH 2  --CH 2  --O--)] q  --H, (b) at least one polyhydroxy compound selected from the group consisting of (I) a linear or branched aliphatic polyhydroxy compound of the formula (2): R 1  --(OH--) x  or a polyether polyol or polyester polyol derived therefrom, and (ii) a cycloaliphatic polyol selected from the group polyhydroxy-C 5  -C 8  -cycloalkane and unsubstituted mono- or disaccharide, (c) at least one di- or polyisocyanate of the formula (3): R 2  --(NCO) y , (d) at least one ethylenically unsaturated monisocyanate of formula (4), or an ethylenically unsaturated acid halide of formula (4&#39;), and optionally further copolymerizable monomers, wherein the variables have the significances given in the claims, in the absence or presence of an additional vinylic comonomer. ##STR1##

The present invention relates to specific branched polyurethane(meth)acrylates, processes for the production thereof, and mouldedophthalmic articles containing them, especially contact lenses.

Polymerisable urethane resins containing inorganic fillers, which arethe reaction product of an ethylenically unsaturated polyisocyanatecomponent with an ethylenically unsaturated polyol, and the thermalcrosslinking of them into moulded articles, are already known e.g. fromJP-A-3-210317. In addition, polymerisable resins which are the additionproduct of an unsaturated isocyanate with an amino-group-containingurethane are known e.g. from JP-A-7-292046. EP-A-0537877 disclosesmacromers which are obtainable e.g. by reacting a compound, which may beobtained from an ethylenically unsaturated isocyanate, a polyalkyleneglycol and a diisocyanate, and which still has a free isocyanate groupat its disposal, with a sugar derivative whose hydroxy groups are atleast partly alkoxylated with an alkylene oxide, and also ophthalmiclenses that are obtainable from these macromers by crosslinking.

Now, surprisingly, new branched polyurethane (meth)acrylates have beenfound, which can be crosslinked in a particularly simple manner, e.g.directly from aqueous solution or solvent-free, to form mouldedophthalmic articles, such as contact lenses.

The present invention relates to ophthalmic mouldings, which areobtainable by crosslinking a prepolymer which is the copolymerisationproduct of

(a) at least one polyalkylene glycol of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --(CHY.sub.3 --CHY.sub.4 --O).sub.p --H                   (1)

or

    HO--[(CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --O--].sub.q --H(1'),

wherein one of radicals Y₁ and Y₂ signifies methyl and the othersignifies hydrogen, one of radicals Y₃ and Y₄ is ethyl and the other ishydrogen, q is a number from 1 to 50, and n, m and p, independently ofone another, are each a number from 0 to 100, wherein the sum of (n+m+p)is 5 to 100,

(b) at least one polyhydroxy compound selected from the group consistingof

(i) a linear or branched aliphatic polyhydroxy compound of formula

    R.sub.1 --(OH).sub.x                                       (2),

wherein R₁ is the radical of a multi-functional linear or branchedaliphatic alcohol and x is a number≧3,

(ii) a polyether polyol, which is the polymerisation product of acompound of formula (2) and a glycol,

(iii) a polyester polyol, which is the polymerisation product of acompound of formula (2), a dicarboxylic acid or a derivative thereof anda diol, and

(iv) a cycloaliphatic polyol selected from the group consisting of a C₅-C₈ -cycloalkane, which is substituted by≧3 hydroxy groups, and anunsubstituted mono- and disaccharide,

(c) at least one di- or polyisocyanate of formula

    R.sub.2 --(NCO).sub.y                                      (3)

wherein R₂ is the radical of an aliphatic, cycloaliphatic,aliphatic-cycloaliphatic, aromatic or araliphatic di- or polyisocyanateand y is a number from 2 to 6,

(d) at least one ethylenically unsaturated monoisocyanate of formula##STR2## or an ethylenically unsaturated acid halide of formula ##STR3##wherein R₃ is hydrogen or methyl, z and z1 independently of one anothersignify the number 0 or 1, B signifies C₁ -C₆ -alkylene, or phenylene orC₇ -C₁₂ -araikylene which is each unsubstituted or substituted by C₁ -C₄-alkyl or C₁ -C₄ -alkoxy, or a radical of formula ##STR4## B₁ signifieslinear or branched C₂ -C₁₂ -alkylene which is optionally interrupted byone or more oxygen atoms, B₂ is C₁ -C₆ -alkylene and X signifieshalogen,

and optionally one or more further copolymerisable monomers, in theabsence or presence of an additional vinylic comonomer.

In formula (1), n, m and p, independently of one another, preferablyeach denote a number from 0 to 50, whereby the sum of (n+m+p) is 8 to50. Most preferably, n, m and p, independently of one another, eachdenote a number from 0 to 25, whereby the sum of (n+m+p) is 9 to 25. Informula (1'), q preferably signifies a number from 1 to 20.

The polyalkylene glycol according to (a) is e.g. a polyethylene glycol,polypropylene glycol, polyethylene glycol/polypropylene glycol blockpolymer, polyethylene glycol/polypropylene glycol/polybutylene glycolblock polymer or a polytetrahydrofuran.

Preferred embodiments of the polyalkylene glycol according to (a) arerepresented by:

(I) compounds of formula (1), wherein p is 0, n and m, independently ofone another, are each a number from 0 to 100, preferably 0 to 50, andmost preferably 0 to 25, and the sum of (n+m) is 5 to 100, preferably 8to 50, most preferably 9 to 25.

(ii) compounds of formula (1), wherein p and m are each 0 and nsignifies a number from 5 to 100, preferably 8 to 50, most preferably 9to 25.

R₁ in formula (2) signifies e.g. the radical of an aliphatic polyol with2 to 18, preferably 3 to 12, most preferably 3 to 8 carbon atoms. Thevariable x preferably signifies a number from 3 to 12, preferably anumber from 3 to 8, most preferably a number from 3 to 6, andparticularly preferably the number 3.

Examples of suitable polyhydroxy compounds of formula (2) are glycerol,diglycerol, triglycerol, 1,1,1-trishydroxymethylethane,1,1,1-trishydroxymethylpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol,erythritol, pentaerythritol, di- or tripentaerythritol, arabitol,sorbitol, disorbitol or mannitol and mixtures thereof. Preferredcompounds of formula (2) are glycerol, 1,1,1 -tris-hydroxymethylpropane,1,2,4-butanetriol, erythritol, pentaerythritol, arabitol or sorbitol. Agroup of especially preferred compounds of formula (2) comprisesglycerol, 1,1,1-trihydroxymethyl-propane and pentaerythritol.

Further suitable as a polyhydroxy compound according to (b) are reactionproducts of the above-mentioned polyhydroxy compounds of formula (2)with a dicarboxylic acid or with a derivative of a dicarboxylic acid,e.g. a dicarboxylic acid anhydride, ester or halide, as well as a diol,whereby oligomeric polyester polyols are obtained, or reaction productsof the above-mentioned polyhydroxy compounds with a glycol, wherebyoligomeric polyether polyols are obtained.

If the polyhydroxy compound according to (b) in question is a polyesterpolyol, then this is preferably an oligomeric reaction product of acompound of formula (2), wherein the above-mentioned meanings andpreferences apply, with an aliphatic or cycloaliphatic dicarboxylic acidhaving 3 to 12 carbon atoms, or an aromatic dicarboxylic acid having 5to 15 carbon atoms, or an appropriate derivative thereof, e.g. acorresponding dicarboxylic acid anhydride, ester or halide, as well as adiol as chain extender. Examples of suitable dicarboxylic acids aremalonic acid, succinic acid, 2,2-dimethylsuccinic acid, glutaric acid,adipic acid, pimelic acid, sebacic acid, tetrahydrophthalic acid,hexahydrophthalic acid, phthalic acid, isophthalic acid, terephthalicacid, maleic acid or fumaric acid, as well as the correspondingdicarboxylic acid esters, halides or anhydrides. Appropriate diols aree.g. linear or branched C₂ -C₂₀ -alkyl-diols; compounds of theabove-mentioned formula (1), wherein Y₁ and Y₂ have the above-mentionedmeanings, p is 0, m and n, independently of one another, each signify anumber from 0 to 10, and the sum of (n+m) is 3 to 10; as well asaromatic-aliphatic diols with 7 to 20 C-atoms.

If the polyhydroxy compound according to (b) in question is a polyetherpolyol, then this is preferably a short-chained polymerisate consistingof a compound of formula (2), wherein the above-mentioned significancesand preferences apply, and ethylene glycol, propylene glycol or amixture thereof.

The above-described polyester polyols and polyether polyols areavailable commercially, e.g. as Desmophen® types, e.g. as Desmophen®650, 670, 550U, 250U.

If the polyhydroxy compound according to (b) in question is acycloaliphatic polyol, then this may be e.g. cyclopentane or preferablya cyclohexane, which is respectively substituted by 3 to 5 andpreferably by 3 or 4 hydroxy groups and bears no further substituents orhetero atoms. Further suitable cycloaliphatic polyols according to (b)are represented by unsubstituted mono- or disaccharides, e.g. glucose,fructose, mannose, galactose, maltose, lactose or saccharose.

In formula (3), R₂ signifies e.g. the radical of a linear or branchedaliphatic polyisocyanate with 3 to 24 C-atoms, the radical of acycloaliphatic or aliphatic-cycloaliphatic polyisocyanate with 3 to 24C-atoms, or the radical of an aromatic or araliphatic polyisocyanatewith 6 to 24 C-atoms. The variable y preferably signifies a number from2 to 4, most preferably the number 2.

The polyisocyanate according to (c) in question is preferably adiisocyanate of formula

    OCN--R.sub.2 --NCO,                                        (3a),

wherein R₂ signifies linear or branched C₃ -C₁₈ -alkylene, orunsubstituted or C₁ -C₄ -alkyl-substitut or C₁ -C₄ -alkoxy-substitutedC₆ -C₁₀ -arylene, C₇ -C₁₈ -aralkylene, C₆ -C₁₀ -arylene-C₁ -C₂-alkylene-C₆ -C₁₀ -arylene, C₃ -C₈ -cycloalkylene, C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene, C₃ -C₈ -cycloalkylene-C₁ -C₂-alkylene-C₃ -C₈ -cycloalkylene or C₁ -C₆ -alkylene-C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene.

R₂ as alkylene preferably signifies a linear or branched C₃ -C₁₈-alkylene radical, more preferably a linear or branched C₄ -C₁₂-alkylene radical, and most preferably a linear or branched C₆ -C₁₀-alkylene radical. A few preferred alkylene radicals are 1,4-butyiene,2,2-dimethyl-1,4-butylene, 1,5-pentylene, 2,2-dimethyl-1,5-pentylene,1,6-hexylene, 2,2,3- or 2,2,4-trimethyl-1,5-pentylene,2,2-dimethyl-1,6-hexylene, 2,2,3- or 2,2,4- or2,2,5-trimethyl-1,6-hexylene, 2,2-dimethyl-1,7-heptylene, 2,2,3- or2,2,4- or 2,2,5- or 2,2,6-trimethyl-1,7-heptylene, 1,8-octylene,2,2-dimethyl-1,8-octylene or 2,2,3- or 2,2,4- or 2,2,5- or 2,2,6- or2,2,7-trimethyl-1,8-octylene.

If R₂ is arylene, this is preferably naphthylene and most preferablyphenylene. If the arylene is substituted, a substituent is preferablylocated in ortho position to an isocyanate group. Examples ofsubstituted arylene are 1-methyl-2,4-phenylene,1,5-dimethyl-2,4-diphenylene, 1-methoxy-2,4-phenylene or1-methyl-2,7-naphthylene.

R₂ as aralkylene is preferably naphthylalkylene and most preferablyphenylalkylene. The alkylene group in aralkylene preferably contains 1to 12, most preferably 1 to 6 and particularly preferably 1 to 4C-atoms. The alkylene group in aralkylene is most particularly methyleneor ethylene. A few examples are 1,3- or 1,4-benzylene,naphth-2-yl-7-methylene, 6-methyl-1,3- or -1,4-benzylene, 6-methoxy-1,3-or -1,4-benzylene.

If R₂ is cycloalkylene, it is preferably C₅ -C₆ -cycloalkylene and mostpreferably cyclohexylene which is respectively unsubstituted ormethyl-substituted. A few examples are 1,3-cyclobutylene,1,3-cyclopentylene, 1,3- or 1,4-cyclohexylene, 1,3- or1,4-cycloheptylene, 1,3- or 1,4- or 1,5-cyclooctylene,4-methyl-1,3-cyclopentylene, 4-methyl-1,3-cyclohexylene,4,4-dimethyl-1,3-cyclohexylene, 3-methyl- or3,3-dimethyl-1,4-cyclohexyl, 3,5-dimethyl-1,3-cyclohexylene,2,4-dimethyl-1,4-cyclohexylene.

If R₂ signifies cycloalkylene-alkylene, it is preferablycyclopentylene-C₁ -C₄ -alkylene, and especially cyclohexylene-C₁ -C₄-alkylene, which is respectively unsubstituted or substituted once orseveral times by C₁ -C₄ -alkyl, especially methyl. The groupcycloalkylene-alkylene preferably denotes cyclohexylene-ethylene andmost preferably denotes cyclohexylene-methylene, which is respectivelyunsubstituted in the cyclohexylene radical or substituted by 1 to 3methyl groups. A few examples are cyclopent-1-yl-3-methylene,3-methyl-cyclopent-1-yl-3-methylene, 3,4-dimethyl-cyclopent-1-yl-3-methylene, 3,4,4-trimethyl-cyclopent-1-yl-3-methylene,cyclohex-1-yl-3- or -4-methylene, 3- or 4- or 5-methyl-cyclohex-1-yl-3-or -4-methylene, 3,4- or 3,5-dimethyl-cyclohex-1-yl-3- or -4-methylene,3,4,5- or 3,4,4- or 3,5,5-trimethyl-cyc-lohex-1-yl-3- or -4-methylene.

If R₂ signifies alkylene-cycloalkylene-alkylene, it is preferably C₁ -C₄-alkylene-cyclopentylene-C₁ -C₄ -alkylene and especially C₁ -C₄-alkylene-cyclohexylene-C₁ -C₄ -alkylene, which is respectivelyunsubstituted or substituted once or several times by C₁ -C₄ -alkyl,most preferably methyl. The group alkylene-cycloalkylene-alkylenepreferably denotes ethylene-cyclohexylene-ethylene and most preferablymethylene-cyclohexylene-methylene, which is respectively unsubstitutedin the cyclohexylene radical or substituted by 1 to 3 methyl groups. Afew examples are cyclopentane-1,3-dimethylene,3-methyl-cyclopentane-1,3-dimethylene3,4-dimethyl-cyclopentane-1,3-dimethylene,3,4,4-trimethyl-cyclopentane-1,3-dimethylene, cyclohexane-1,3- or-1,4-dimethylene, 3- or 4- or 5-methyl-cyclohexane-1,3- or-1,4-dimethy-lene, 3,4- or 3,5-dimethyl-cyclohexane-1,3- or-1,4-dimethylene, 3,4,5- or 3,4,4- or 3,5,5-trimethyl-cyclohexane-1,3-or -1,4-dimethylene.

When R₂ is C₃ C₈ -cycloalkylene-C₁ -C₂ -alkylene-C₃ -C₈ -cycloalkyleneor C₆ -C₁₀ -arylene-C₁ C₂ -alkylene-C₆ -C₁₀ -arylene it is preferably C₅-C₆ -cycloalkylene-methylene-C₅ -C₆ -cycloalkylene orphenylene-methylene-phenylene, which may respectively be unsubstitutedin the cycloalkyl or phenyl ring or substituted by one or more methylgroups.

The radical R₂ in formula (3a) has symmetrical or asymmetricalstructure.

One preferred group of polyisocyanates according to (c) comprisescompounds of formula (3a), wherein R₂ signifies linear or branched C₆-C₁₀ -alkylene, cyclohexylene-methylene orcyclohexylene-methylene-cyclohexylene which are either unsubstituted orsubstituted in the cyclohexyl moiety by 1 to 3 methyl groups, orphenylene or phenylene-methylene-phenylene which are eitherunsubstituted or substituted in the phenyl moiety by methyl.

Examples of especially preferred polyisocyanates of formula (3) or (3a)according to (c) are isophorone diisocyanate (IPDI),toluylene-2,4-diisocyanate (TDI), methylenebis(cyclohexyl-isocyanate),1,6-diisocyanato-2,2,4-trimethyl-n-hexane (TMDI),methylenebis(phenyl-isocyanate) or hexamethylene-diisocyanate (HMDI).

In formulae (4) and (4'), R₃, independently of one another, each signifyhydrogen or preferably methyl.

The variable z is e.g. the number 0 or preferably the number 1. Thevariable z1 signifies e.g. the number 1 and preferably the number 0.

When B and B₂ are alkylene, they are each, independently of one another,e.g. 1-methyl- or 1,1 -dimethyl-methylene, 1,2-ethylene, 1,2- or1,3-propylene, 2-methyl-propylene or 1,2-, 1,3-, 1,4- or 2,3-butylene,2,2-dimethyl-1,3-propylene, 2-methyl- or 2,3-dimethyl-1,4-butylene,1,2-, 1,3-, 1,4- or 1,5-pentylene, 2-methyl- or 3-methyl- or4-methylpentylene or 1,2-, 1,3-, 1,4-, 1,5- or 1,6-hexylene. B and B₂ asalkylene are each, independently of one another, preferably C₁ -C₄-alkylene and most preferably methylene.

When B is a phenylene radical, it is e.g. 1,2-, 1,3- or 1,4-phenyleneeither unsubstituted or substituted by methyl or methoxy. B as aphenylene radical is preferably 1,3- or 1,4-phenylene.

When B is an aralkylene radical, it is e.g. benzylene which is eitherunsubstituted or substituted by methyl or methoxy, whereby the methylenegroup is respectively bonded to nitrogen isocyanate. B as an aralkyleneradical is preferably the 1,3- or 1,4-phenylenemethylene radical,whereby the methylene group is respectively bonded to the nitrogenisocyanate.

If B signifies a radical of the above-mentioned formula (5), then B₁ asalkylene may be e.g. one of the C₂ -C₁₂ -alkylene radicals alreadymentioned for R₂ or B.

Examples of B₁ as alkylene which is interrupted by oxygen atoms are--CH₂ CH₂ --O--CH₂ CH₂ --, --CH₂ CH₂ --O--CH₂ CH₂ --O--CH₂ CH₂ --, --CH₂CH₂ --O --CH₂ CH₂ --O--CH₂ CH₂ ----O--CH₂ CH₂ --,--CH(CH₃)CH₂--O--CH(CH₃)CH₂ --, --CH(CH₃)CH₂ --O--CH₂ CH₂ --, --CH(C₂ H₅)CH₂--O--CH₂ CH₂ --, --CH(C₂ H₅)CH₂ --O--CH(C₂ H₅)CH₂ -- or --CH₂ CH₂ CH₂CH₂ --O--CH₂ CH₂ CH₂ CH₂ --.

B₁ preferably signifies linear or branched C₂ -C₈ -alkylene, mostpreferably linear C₂ -C₈ -alkylene, and particularly preferably linearC₂ -C₄ -alkylene. In a preferred embodiment of the invention, B₁signifies 1,2-ethylene.

B preferably signifies a radical of the above-mentioned formula (5),wherein for the variable B₁ contained therein, the above-mentionedmeanings and preferences apply.

X signifies e.g. bromine or preferably chlorine. ##STR5## wherein R₃ ishydrogen or methyl, B₁ signifies linear or branched C₂ -C₈ -alkylene, B₂is C₁ -C₄ -alkylene, z1 signifies the number 0 or 1 and X representshalogen, are preferred as component (d) of the prepolymers according tothe invention.

Compounds of the above-mentioned formulae (4'a) or especially (4a),wherein R₃ is hydrogen or methyl, B₁ is linear or branched C₂ -C₄-alkylene, z1 is the number 0 and X represents bromine or chlorine, areespecially preferred as component (d) of the prepolymers according tothe invention.

If, in order to produce the prepolymers used according to the invention,further copolymerisable monomers are used as well as components (a)-(d)mentioned above, then these may be in principle all monomers that canform copolymers with di- or poly-isocyanates or di- or polyhydroxycompounds, for example further hydroxy compounds, e.g. ethylenicallyunsaturated monohydroxy compounds such as 2-hydroxyethyl acrylate or2-hydroxyethyl methacrylate. However, it is preferable if no furthercomonomers are used in the production of the prepolymers according tothe invention, apart from the said components (a)-(d).

One preferred embodiment of the prepolymers used according to theinvention relates to those which are the polymerisation product of

(a) one or more polyalkylene glycols of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --H(1 a),

wherein one of radicals Y₁ and Y₂ signifies methyl and the other radicalsignifies hydrogen,

and n and m, independently of one another, each denote a number from 0to 50,

wherein the sum of (n+m) is 8 to 50,

(b) one or more linear or branched aliphatic polyhydroxy compounds offormula

    R.sub.1 --(OH).sub.x                                       (2)

wherein R₁ is the radical of a multi-functional aliphatic alcohol and xis a number from 3 to 8,

(c) one or more diisocyanates of formula

    OCN--R.sub.2 --NCO                                         (3a),

wherein R₂ signifies linear or branched C₃ -C₁₈ -alkylene orunsubstituted or C₁ -C₄ -alkyl-substituted or C₁ -C₄ -alkoxy-substitutedC₆ -C₁₀ -arylene, C₇ -C₁₈ -aralkylene, C₆ -C₁₀ -arylene-C₁ -C₂-alkylene-C₆ -C₁₀ -arylene, C₃ -C₈ -cycloalkylene, C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene, C₃ -C₈ -cycloalkylene-C₁ -C₂-alkylene-C₃ -C₈ -cycloalkylene or C₁ -C₆ -alkylene-C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene, and

(d) one or more ethylenically unsaturated compounds of formula ##STR6##wherein R₃ is hydrogen or methyl, B₁ signifies linear or branched C₂ -C₈-alkylene, B₂ is C₁ -C₄ -alkylene, z1 signifies the number 0 or 1 and Xrepresents halogen.

An especially preferred embodiment of the prepolymers used according tothe invention relates to those which are the polymerisation product of

(a) one or more polyalkylene glycols of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --H(1a),

wherein one of radicals Y₁ and Y₂ signifies methyl and the other radicalsignifies hydrogen,

and n and m, independently of one another, each denote a number from 0to 25,

wherein the sum of (n+m) is 9 to 25,

(b) one or more polyhydroxy compounds selected from the group consistingof glycerol, diglycerot, triglycerol, 1,1,1 -trishydroxymethylethane,1,1,1-trishydroxymethylpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol,erythritol, pentaerythritol, di- and tripentaerythritol, arabitol,sorbitol, disorbitol and mannitol and mixtures thereof,

(c) a diisocyanate of formula

    OCN--R.sub.2 --NCO                                         (3a),

wherein R₂ signifies linear or branched C₆ -C₁₀ -alkylene,cyclohexylene-methylene or cyclohexylene-methylene-cyclohexylene eitherunsubstituted or substituted in the cyclohexyl moiety by 1 to 3 methylgroups, or phenylene or phenylene-methylene-phenylene eitherunsubstituted or substituted in the phenyl moiety by methyl, and

(d) an ethylenically unsaturated compound of the above-mentioned formula(4a), wherein R₃ denotes hydrogen or methyl and B₁ signifies linear orbranched C₂ -C₄ alkylene.

The prepolymers which are the copolymerisation product consisting of theabove-mentioned components (a), (b), (c) and (d), whereby theabove-mentioned meanings and preferences apply, are new and represent afurther object of the invention.

The prepolymers according to the invention may be produced e.g. wherebythe above-mentioned components (a), (b), (c) and (d) and optionallyfurther copolymerisable monomers are reacted together in any sequence inan inert solvent at a temperature of e.g. -5° C. to 150° C.

Suitable inert solvents are aprotic, preferably polar solvents, forexample hydrocarbon halides (chloroform, methylene chloride,trichloroethane, tetrachloroethane, chlorobenzene), ethers(tetrahydrofuran, dioxane), ketones (acetone, ethyl methyl ketone,dibutyl ketone, methyl isobutyl ketone), carboxylic acid esters andlactones (ethyl acetate, butyrolactone, valerolactone), alkylatedcarboxylic acid amides (N,N-dimethylacetamide, N-methylpyrrolidone),nitriles (acetonitrile), sulphones and sulphoxides (dimethyl sulphoxide,tetramethylene sulphone). Polar solvents are preferably employed.

If the prepolymer consists of components (a), (b), (c) and (d), thereactants are employed e.g. in quantities of

    ______________________________________                                        1         OH equivalent of component (a),                                       0.05-1 OH equivalents of component (b),                                        0.5-1.95 NCO equivalents of component (c), and                                0.1-2 NCO or acid halide equivalents of component (d).                     ______________________________________                                    

It is preferable to produce prepolymers by using

    ______________________________________                                        1         OH equivalent of component (a),                                       0.1-0.8 OH equivalents of component (b),                                      0.6-1.5 NCO equivalents of component (c), and                                 0.1-1.5 NCO or acid halide equivalents of component (d).                    ______________________________________                                    

It is especially preferable to produce prepolymers by using

    ______________________________________                                        1         OH equivalent of component (a),                                       0.2-0.5 OH equivalents of component (b),                                      0.8-1.4 NCO equivalents of component (c), and                                 0.1-1 NCO or acid halide equivalents of component (d).                      ______________________________________                                    

The stoichiometry is advantageously chosen so that the sum of OHequivalents of components (a) and (b) is greater than the number of NCOequivalents of component (c). It is further preferred for the sum of OHequivalents of components (a) and (b) to be equal to or greater than,preferably approximately equal to, the sum of NCO and acid halideequivalents of components (c) and (d).

Components (a)-(d) are all known compounds or compound mixtures, or maybe obtained in accordance with methods known per se.

The reaction temperature is e.g. -5° C. to 150° C., preferably 0 to 100°C., most preferably 0 to 80° C., and particularly preferably 15 to 50°C. Furthermore, it is preferable for the reaction of thehydroxy-group-containing components (a) and (b) with theisocyanate-group-containing components (c) and (d) to be carried out inthe presence of a catalyst. Suitable catalysts are for example metalsalts such as alkali metal salts or tin salts of organic carboxylicacids, or tertiary amines, for example (C₁ -C₆ -alkyl)₃ N(triethylamine, tri-n-butylamine), N-methylpyrrolidine,N-methylmorpholine, N,N-dimethylpiperidine, pyridine and1,4-diaza-bicyclooctane. Tin salts have proved to be particularlyeffective, especially alkyl-tin salts of carboxylic acids, for exampledibutyl tin dilaurate and tin dioctoate.

The catalyst is employed in the reaction e.g. in a molar ratio of 1:10to 1:1000, preferably 1:50 to 1:750, most preferably ca. 1:100 to 1:500,respectively based on component (a).

The reaction times may vary within a broad range, whereby progress ofthe reaction can be followed well by monitoring the reduction of theisocyanate content in the reaction mixture. As a rule, reaction times of1 to 24 hours, preferably 4 to 16 hours, are sufficient to achieve acomplete reaction.

Isolation and purification of the produced compounds are effected byknown processes, for example extraction, crystallisation,recrystallisation, ultrafiltration or by chromatographic purificationmethods. The compounds are obtained in high yields and high purity.

It is advantageous to react a mixture of the above-mentioned components(a) and (b) either with a mixture of components (c) and (d) orpreferably first of all with component (c) and then with component (d).

One preferred embodiment of the present invention relates to a processfor the production of prepolymers, which is characterised in that amixture of components (a) and (b) is firstly allowed to react withcomponent (c), and afterwards is reacted without intermediate isolationwith component (d), as well as the prepolymers obtainable in this way.

A further preferred embodiment of the present invention relates to aprocess for the production of crosslinkable prepolymers, which ischaracterised in that a mixture of 1 OH equivalent of component (a) and0.05 to 1 OH equivalents of component (b) is reacted in an inert solventat a temperature of 0 to 100° C. in the presence of a catalyst eitherwith a mixture of 0.5 to 1.95 NCO equivalents of a component (c) and 0.1to 2 NCO or acid halide equivalents of a component (d) or first of allwith 0.5 to 1.95 NCO equivalents of a component (c) and then with 0.1 to2 NCO or acid halide equivalents of a component (d), wherein forcomponents (a), (b), (c) and (d) the above-mentioned meanings andpreferences apply, as well as the crosslinkable prepolymers obtainableby the process.

An especially preferred embodiment of the present invention relates to aprocess for the production of crosslinkable prepolymers, which ischaracterised in that a mixture of 1 OH equivalent of component (a) and0.1 to 0.8 OH equivalents of component (b) is reacted, in an inertsolvent at a temperature of 0 to 80° C., in the presence of a catalystselected from the group of metal salts of organic carboxylic acids andtertiary amines, first of all with 0.6 to 1.5 NCO equivalents ofcomponent (c) and then with 0.1 to 1.5 NCO or acid halide equivalents ofa component (d), wherein for components (a), (b), (c) and (d) theabove-mentioned meanings and preferences apply, as well as thecrosslinkable prepolymers obtainable by the process.

The prepolymers according to the invention are crosslinkable, butuncrosslinked or at least substantially uncrosslinked; nevertheless,they are stable, i.e. spontaneous crosslinking due to homopolymerisationdoes not take place.

The crosslinkable prepolymers which are obtainable by means ofpolymerisation of components (a)-(d), and optionally furthercopolymerisable monomers, are advantageously liquid or readily meltableor water-soluble; the prepolymers which are water-soluble are preferredin particular. The average molecular weight of the prepolymers accordingto the invention may vary within a broad range. An average molecularweight of e.g. 1000 to 50,000 has proved to be advantageous for theprepolymers according to the invention.

Furthermore, the prepolymers according to the invention may be purifiedin a manner known per se, for example by precipitation with acetone,dialysis or ultrafiltration, whereby ultrafiltration is preferred inparticular. As a result of this purification procedure, the prepolymersaccording to the invention may be obtained in extremely pure form, e.g.as solvent-free liquids or melts or as concentrated aqueous solutions,which are free from or at least substantially free from reactionproducts such as salts, and from starting materials or othernon-polymeric constituents.

The preferred purifiying process for the prepolymers according to theinvention, ultrafiltration, may be carried out in a manner known per se.Thus, it is possible to carry out ultrafiltration repeatedly, forexample two to ten times. Alternatively, ultrafiltration may also becarried out continuously, until reaching the desired degree of purity.The desired degree of purity may be basically selected at any level, andis preferably set so that the content of undesired constituents in theprepolymers is e.g.≦0.001%, most preferably≦0.0001% (1 ppm). As a resultof their synthesis, the prepolymers may additionally containconstituents which are acceptable from a physiological point of view,e.g. sodium chloride, whereby such constituents are advantageouslypresent in an amount of≦1%, preferably≦0.1%, most preferably≦0.01%.

As already mentioned above, the prepolymers according to the inventionmay be crosslinked in an extremely effective and well-directed manner,in particular by photo-crosslinking. Crosslinking may take place in thepresence or preferably in the absence of an additional vinyliccomonomer. The crosslinked polymers are insoluble in water.

In the case of photo-crosslinking, a photo-initiator is suitably addedwhich can initiate radical crosslinking. Examples of these are familiarto the person skilled in the art, and suitable photo-initiators whichmay be mentioned in particular are benzoin-methylether,1-hydroxycyclohexyl-phenylketone, Darocure® 1173 or Irgacure® types.Crosslinking may be commenced by actinic radiation, e.g. UV light, or byionised radiation, e.g. gamma rays or X-rays.

Photopolymerisation may also be carried out without adding a solvent,e.g. if the prepolymer is a liquid or readily meltable prepolymer, or ittakes place in a suitable solvent. Suitable solvents are basically allsolvents that dissolve the polymers according to the invention and theoptionally additionally employed vinylic comonomers, e.g. water,alcohols such as lower alkanols, e.g. ethanol or methanol, furthermorecarboxylic acid amides, such as dimethyl-formamide, or dimethylsulphoxide, and likewise mixtures of suitable solvents, e.g. mixtures ofwater with an alcohol, such as a water/ethanol or a water/methanolmixture.

Photo-crosslinking is preferably effected whilst solvent-free oressentially solvent-free or directly from an aqueous solution of theprepolymers according to the invention, which may be obtained as theresult of the preferred purification step, ultrafiltration, optionallyafter adding an additional vinylic comonomers. For example,photo-crosslinking may be undertaken from a 15 to 90% aqueous solution.

The process for the production of the crosslinked polymers according tothe invention can be characterised e.g. in that a prepolymer, which is apolymerisation product obtainable as described above from components(a), (b), (c) and (d) and optionally further copolymerisable monomers,especially in substantially pure form, i.e. for example afterultrafiltration once or several times, is photo-crosslinked whilstsolvent-free or substantially solvent-free or in solution, especially inaqueous solution, in the presence or preferably in the absence of anadditional vinylic comonomer, preferably using a photoinitiator.

The vinylic comonomer which may be additionally used forphoto-crosslinking in accordance with the invention may be hydrophilic,hydrophobic or may be a mixture of a hydrophobic and a hydrophilicvinylic monomer. Suitable vinylic monomers include especially thosenormally used for the manufacture of contact lenses. By a hydrophilicvinylic monomer is understood a monomer which as a homopolymer typicallyyields a polymer that is water-soluble or can absorb at least 10 percentby weight water. In analogous manner, by a hydrophobic vinylic monomeris understood a monomer which as a homopolymer typically yields apolymer that is insoluble in water and can absorb less than 10 percentby weight water.

It is preferable to use a hydrophobic vinylic comonomer, or a mixture ofa hydrophobic vinylic comonomer with a hydrophilic vinylic comonomer,whereby this mixture contains at least 50 percent by weight of ahydrophobic vinyl comonomer. In this way, the mechanical properties ofthe polymer may be improved without the water content droppingsubstantially. What basically applies is that both conventionalhydrophobic vinylic comonomers and conventional hydrophilic vinyliccomonomers are suitable for copolymerisation with the prepolymersaccording to the invention.

Suitable hydrophobic vinylic comonomers include, without this being adefinitive list, C₁ -C₁₈ -alkylacrylates and -methacrylates, C₃ -C₁₈alkylacrylamides and -methacrylamides, acrylonitrile, methacrylonitrile,vinyl-C₁ -C₁₈ -alkanoates, C₂ -C₁₈ -alkenes, C₂ -C₁₈ -halo-alkenes,styrene, C₁ -C₆ -alkylstyrene, vinylalkylethers in which the alkylmoiety has 1 to 6 carbon atoms, C₂ -C₁₀ -perfluoralkyl-acrylates and-methacrylates or correspondingly partially fluorinated acrylates andmethacrylates, C₃ -C₁₂-perfluoralkyl-ethyl-thiocarbonylaminoethyl-acrylates and-methacrylates, acryloxy and methacryloxy-alkylsiloxanes,N-vinylcarbazole, C₁ -C₁₂ -alkylesters of maleic acid, fumaric acid,itaconic acid, mesaconic acid and the like. Preference is given e.g. toC₁ -C₄ -alkylesters of vinylically unsaturated carboxylic acids with 3to 5 carbon atoms or vinylesters of carboxylic acids with up to 5 carbonatoms.

Examples of suitable hydrophobic vinylic comonomers includemethylacrylate, ethylacrylate, propylacrylate, isopropylacrylate,cyclohexylacrylate, 2-ethylhexylacrylate, methylmethacrylate,ethylmethacrylate, propylmethacrylate, vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, styrene, chloroprene, vinyl chloride,vinylidene chloride, acrylonitrile, 1-butene, butadiene,methacrylonitrile, vinyl toluene, vinyl ethyl ether,perfluorohexylethyl-thiocarbonyl-aminoethyl-methacrylate, isobornylmethacrylate, trifluoroethyl methacrylate, hexafluoro-isopropylmethacrylate, hexafluorobutyl methacrylate,tris-trimethylsilyloxy-silyl-propyl methacrylate,3-methacryloxypropyl-pentamethyl-disiloxane andbis(methacryloxypropyl)-tetramethyl-disiloxane.

Suitable hydrophilic vinylic comonomers include, without this being adefinitive list, hydroxy-substituted lower alkylacrylates and-methacrylates, acrylamide, methacrylamide, lower alkyl-acrylamides and-methacrylamides, ethoxylated acrylates and methacrylates,hydroxy-substituted lower alkyl-acrylamides and -methacrylamides,hydroxy-substituted lower alkylvinyl-ethers, sodium ethylene sulphonate,sodium styrene sulphonate, 2-acrylamido-2-methyl-propane-sulphonic acid,N-vinyl pyrrole, N-vinyl succinimide, N-vinyl pyrrolidone, 2- or 4-vinylpyridine, acrylic acid, methacrylic acid, amino- (whereby the term"amino" also includes quaternary ammonium), mono-lower-alkylamino- ordi-lower-alkylamino-lower-alkyl-acrylates and -methacrylates, allylalcohol and the like. Preference is given e.g. to hydroxy-substituted C₂-C₄ -alkyl(meth)acrylates, five- to seven-membered N-vinyl-lactams,N,N-di-C₁ -C4-alkyl-(meth)acrylamides and vinylically unsaturatedcarboxylic acids with a total of 3 to 5 carbon atoms.

Examples of suitable hydrophilic vinylic comonomers include hydroxyethylmethacrylate, hydroxyethyl acrylate, acrylamide, methacrylamide,dimethylacrylamide, allyl alcohol, vinyl pyridine, vinyl pyrrolidone,glycerol methacrylate, N-(1,1-dimethyl-3-oxobutyl)acrylamide, and thelike.

Preferred hydrophobic vinylic comonomers are methyl methacrylate andvinyl acetate. Preferred hydrophilic vinylic comonomers are2-hydroxyethyl methacrylate, N-vinyl pyrrolidone and acrylamide.

The processing according to the invention of the prepolymers intomoulded ophthalmic articles, especially contact lenses, may take placein a manner known per se, for example whereby photo-crosslinking of theprepolymers according to the invention takes place in an appropriatecontact lens mould. Further examples of moulded articles according tothe invention, apart from contact lenses, are e.g. intra-occular lensesor eye dressings, furthermore biomedicinal articles which may be used insurgery, such as heart valves, artificial arteries or the like, alsofilms or membranes, e.g. membranes for diffusion control,photo-structurable films for data storage, or photo resist materials,e.g. membranes or moulded articles for etch resist printing or screenresist printing.

One preferred process for the production of an ophthalmic moulding ischaracterised in that it comprises the following steps:

a) introducing a prepolymer, which is obtainable as depicted above fromcomponents (a), (b), (c) and (d) and is liquid or readily meltable atroom temperature, and which is essentially free from solvents, into amould, in the presence or preferably in the absence of an additionalvinylic comonomer, and supplementing with a photo-initiator,

b) initiating the photo-crosslinking,

c) opening the mould, so that the moulding can be removed from themould.

A further preferred process for the production of an ophthalmic mouldingis characterised in that it comprises the following steps:

a) producing a water-soluble prepolymer, which is obtainable as depictedabove from components (a), (b), (c) and (d), in an essentially aqueoussolution, in the presence or preferably in the absence of an additionalvinylic comonomer, and supplementing with a photo-initiator,

b) introducing the solution obtained into a mould,

c) initiating the photo-crosslinking,

d) opening the mould, so that the moulding can be removed from themould.

The prepolymers according to the invention may be introduced into amould by methods known per se, especially conventional dispensing, e.g.dropwise addition. If vinylic comonomers are present, the comonomersemployed are those mentioned above, in the quantities depicted above.Any vinylic comonomers that are optionally present are advantageouslyfirst of all mixed with the prepolymer according to the invention andthen introduced into the mould.

Appropriate moulds are made for example from polypropylene. Suitablematerials for re-usable mounds are e.g. quartz, sapphire glass ormetals.

If the moulded articles to be produced are contact lenses, these may beproduced in a manner known per se, e.g. in a conventional "spin-castingmould", as described for example in U.S. Pat. No. 3,408,429, or by theso-called full mould process in a static form, as described e.g. in U.S.Pat. No. 4,347,1 98.

Photo-crosslinking may be initiated in the mould e.g. by means ofactinic radiation, such as UV light, or ionising radiation, such asgamma radiation or X-rays.

As already mentioned, photo-crosslinking is advantageously carried outin the presence of a photo-initiator which can initiate radicalcrosslinking. The photo-initiator is advantageously added to theprepolymers according to the invention prior to introducing them intothe mould, preferably by mixing the polymers and the photo-intiatortogether. The amount of photo-initiator may be selected from a widerange, whereby an amount of up to 0.05 g/g polymer and especially up to0.003 g/g polymer has proved favourable.

What is notable is that the crosslinking according to the invention maybe effected in a very short time, e.g. in≦60 minutes, advantageouslyin≦20 minutes, preferably in≦10 minutes, most preferably in≦5 minutes,particularly preferably in 1 to 60 seconds and most particularly in 1 to30 seconds.

Opening of the mould so that the moulded article can be removed from themound may take place in a manner known per se.

If the moulded article produced according to the invention is a contactlens which was produced solvent-free from an already purified prepolymeraccording to the invention, then after removal of the moulded article,it is not normally necessary to follow up with purification steps suchas extraction. This is because the prepolymers employed do not containany undesired constituents of low molecular weight; consequently, thecrosslinked product is also free or substantially free from suchconstituents and subsequent extraction can be dispensed with.Accordingly, the contact lens can be directly transformed in the usualway, by hydration, into a ready-to-use contact lens. Appropriateembodiments of hydration are known to the person skilled in the art,whereby ready-to-use contact lenses with very varied water content maybe obtained. The contact lens is expanded for example in water, in anaqueous salt solution, especially an aqueous salt solution having anosmolarity of about 200 to 450 milli-osmole in 1000 ml (unit: mOsm/ml),preferably about 250 to 350 mOsm/l and especially about 300 mOsm/l, orin a mixture of water or an aqueous salt solution with a physiologicallycompatible polar organic solvent, e.g. glycerol. Preference is given toexpansions of the prepolymer in water or in aqueous salt solutions.

The aqueous salt solutions used for hydration are advantageouslysolutions of physiologically compatible salts, such as buffer saltsconventionally used in the field of contact lens care, e.g. phosphatesalts, or isotonising agents conventionally used in the field of contactlens care, such as in particular alkali halides, e.g. sodium chloride,or solutions of mixtures thereof. One example of an especially suitablesalt solution is an artificial, preferably buffered lachrymal fluid,which is adapted to natural lachrymal fluid as regards pH value andosmolarity, e.g. an unbuffered or preferably buffered common saltsolution, for example buffered by phosphate buffer, whose osmolarity andpH value correspond to the osmolarity and pH value of human lachrymalfluid.

The above-defined hydration fluids are preferably pure, i.e. free orsubstantially free from undesired constituents. This is most preferablypure water or an artificial lachrymal fluid as described above.

If the moulded article produced according to the invention is a contactlens which was produced from an aqueous solution of an already purifiedprepolymer according to the invention, then the crosslinked product alsodoes not contain any troublesome impurities. It is therefore notnecessary to carry out subsequent extraction. Since crosslinking iscarried out in an essentially aqueous solution, it is additionallyunnecessary to carry out subsequent hydration. The contact lensesobtainable by this process are therefore notable, according to anadvantageous embodiment, for the fact that they are suitable for theirintended usage without extraction. By intended usage is understood, inthis context, that the contact lenses can be used in the human eye.

The contact lenses obtainable according to the invention have a widerange of unusual and extremely advantageous properties. One of theseproperties which may be named is for example its excellent compatabilitywith the human cornea, which is based on a well-balanced relationshipbetween water content, oxygen permeability and mechanical properties.Moreover, the contact lenses according to the invention have highresistance of shape. No changes in shape can be detected even afterautoclaving at e.g. about 120° C.

What is also notable is that the contact lenses according to theinvention, i.e. especially those containing a crosslinked polymerconsisting of a prepolymer that is a polymerisation product of theabove-mentioned components (a), (b), (c) and (d), can be produced in avery simple and efficient way compared with the prior art. This is basedon many factors. On the one hand, the starting materials may be acquiredor produced inexpensively. Secondly, there is the advantage that theprepolymers are surprisingly stable, so that they may undergo a highdegree of purification. Therefore, for crosslinking, a polymer may beused which requires practically no more subsequent purification, such asin particular complicated extraction of unpolymerised constituents.Furthermore, crosslinking may take place solvent-free or in aqueoussolution, so that a subsequent solvent exchange or the hydration step isnot necessary. Finally, photo-polymerisation is effected within a shortperiod, so that from this point of view also the production process forthe contact lenses according to the invention may be set up in anextremely economic way.

Of course, all the above-mentioned advantages apply not only to contactlenses, but also to other moulded articles according to the invention.The total of the different advantageous aspects during production of themoulded articles according to the invention leads to the suitability ofthe moulded articles in particular as mass-produced articles, forexample as contact lenses which are worn for a short time-span and thenreplaced by new lenses.

In the following examples, if not expressly stated otherwise, thequantities given are amounts by weight, and the temperatures are givenin degrees Celsius. The examples are not suitable for limiting theinvention in any way, for example to the scope of the examples.

PREPARATION EXAMPLES Example 1

30 g of polyethylene glycol 600 and 0.67 g of 1,1,1-trimethylol propaneare dissolved in 300 ml of ethyl methyl ketone and heated to ca. 45° C.0.07 g of dibutyl tin dilaurate are added, then 8.35 g of isophoronediisocyanate added dropwise, and stirred for ca. 4 hours at 45° C. Then,6.2 g of isocyanato ethyl methacrylate (IEM) are added and stirringcontinued until the isocyanate content has lowered to 0.04equivalents/kg. The solution is concentrated and the productprecipitated from diethylether as a slightly yellowish oil.

Example 1a

30 g of polyethylene glycol 600 and 0.67 g of 1,1,1-trimethylol propaneare dissolved in 300 ml of tetrahydrofuran and heated to ca. 45° C. 0.07g of dibutyl tin dilaurate are added, then 8.35 g of isophoronediisocyanate are added dropwise, and stirring effected for ca. 4 hoursat 45° C. Then, 4.18 g of methacrylol chloride and 2.8 g oftriethylamine are added and stirring continued until practically no acidchloride can be detected. The solution is concentrated and the productprecipitated from diethylether as a slightly yellowish oil.

Example 2

20 g of polyethylene glycol 1000 and 0.54 g of 1,1,1-trimethylol propaneare dissolved in 250 ml of ethyl methyl ketone and heated to ca. 45° C.0.05 g of dilbutyl tin dilaurate are added, then 4.45 g of isophoronediisocycnate are added dropwise, and stirring effected for ca. 2 hoursat 45° C. Then, 1.86 g of isocyanato ethyl methacrylate (IEM) are addeddropwise, and stirring continued for ca. 10 hours at 45° C. At the end,the solution is concentrated and the product precipitated fromdiethylether as a clear oil which begins to crystallise after some time.

Example 3

6 g of polyethylene glycol 600, 10 g of polyethylene glycol 1000 and0.54 g of 1,1,1-trimethylol propane are reacted with 4.45 g ofisophorone diisocyanate and 1.86 g of isocyanato ethyl methacrylate(IEM) by the method described in example 2. After precipitation fromdiethylether, a clear, viscous oil is obtained.

Example 4

12 g of polyethylene glycol 600 and 0.37 g of glycerol are reacted with3.36 g of hexamethylene diisocyanate and 1.86 g of isocyanato ethylmethacrylate (IEM) by the method described in example 2. Afterprecipitation from diethylether, a clear, viscous oil is obtained.

Application Examples Example 5

1.4 g of the polymer obtained according to example 1 and 4 mg ofIrgacure® 2959 are mixed with 0.6 g of water until a clear homogeneoussolution is obtained. From the clear, viscous solution, a 0.1 mm thickfilm is produced between two glass plates with spacers. The film isexposed to a UV lamp for 10 seconds. A clear, flexible film is obtained,which swells in water to form a clear hydrogel with a solid content of42%. The elasticity module of the swollen film is 1 MPa (measured with atensometer from the company Vitrodyne), and the tensile expansion has avalue of 130%.

By employing the above process with an equivalent amount of the polymerproduced according to example 1a, instead of the polymer obtainedaccording to example 1, a film with equally good properties is obtained.

Example 6

1.4 g of the polymer obtained according to example 2 and 4 mg ofIrgacure® 2959 are mixed with 0.6 g of water until a clear homogeneoussolution is obtained. From the clear, viscous solution, a 0.1 mm thickfilm is produced between two glass plates with spacers. The film isexposed to a UV lamp for 10 seconds. A clear, flexible film is obtained,which swells in water to form a clear hydrogel with a dry content of31%. The elasticity module of the swollen film is 0.8 MPa (measured witha tensometer from the company Vitrodyne), and the tensile expansion hasa value of 140%.

Example 7

From the product according to example 3, a 70% aqueous solution with0.2% by weight Irgacure® 2959 is produced by the method described inexample 1. The film obtained through irradiation for 10 seconds swellsin water to form a hydrogel with 30% dry content. The elasticity moduleof the film is 0.7 MPa, and the tensile expansion is ca. 120%.

Example 8

1.0 g of the polymer obtained according to example 4 and 4 mg ofIrgacure® 2959 are mixed with 1.0 g of water until a clear homogeneoussolution is obtained. From the clear, viscous solution, a 0.1 mm thickfilm is produced between two glass plates with spacers. The film isexposed to a UV lamp for 10 seconds. A clear, flexible film is obtained,which swells in water to form a clear hydrogel with a dry content of26%. The elasticity module of the swollen film is 0.48 MPa (measuredwith a tensometer from the company Vitrodyne), and the tensile expansionhas a value of ca. 110%.

What is claimed is:
 1. Ophthalmic moulding, which is obtained bycrosslinking a prepolymer which is the copolymerisation product of(a) atleast one polyalkylene glycol of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --(CHY.sub.3 --CHY.sub.4 --O).sub.p --H                   (1)

or

    HO--[(CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --O--].sub.q --H(1'),

wherein one of radicals Y₁ and Y2 is methyl and the other is hydrogen,one of radicals Y₃ and Y₄ is ethyl and the other is hydrogen, q is anumber from 1 to 50, and n, m and p, independently of one another, areeach a number from 0 to 100, wherein the sum of (n+m+p) is 5 to 100, (b)at least one polyhydroxy compound selected from the group consistingof(i) a linear or branched aliphatic polyhydroxy compound of formula

    R.sub.1 --(OH).sub.x                                       ( 2),

wherein R₁ is the radical of a multi-functional linear or branchedaliphatic alcohol and x is a number≧3, (ii) a polyether polyol, which isthe polymerisation product of a compound of formula (2) and a glycol,(iii) a polyester polyol, which is the polymerisation product of acompound of formula (2), a dicarboxylic acid or a derivative thereof anda diol, and (iv) a cycloaliphatic polyol selected from the groupconsisting of a C₅ -C8-cyclo-alkane, which is substituted by≧3 hydroxygroups, and an unsubstituted mono- and disaccharide, (c) at least onedi- or polyisocyanate of formula

    R.sub.2 --(NCO).sub.y                                      ( 3)

wherein R₂ is the radical of an aliphatic, cycloaliphatic,aliphatic-cycloaliphatic, aromatic or araliphatic di- or polyisocyanateand y is a number from 2 to 6, (d) at least one ethylenicallyunsaturated monoisocyanate of formula ##STR7## or an ethylenicallyunsaturated acid halide of formula ##STR8## wherein R₃ is hydrogen ormethyl, z and z1, independently of one another, each signify the number0 or 1, B signifies C₁ -C₆ -alkylene, or phenylene or C₇ -C₁₂-aralkylene which is each unsubstituted or substituted by C₁ -C₄ -alkylor C₁ -C₄ -alkoxy, or a radical of formula ##STR9## B₁ signifies linearor branched C₂ -C₁₂ -alkylene which is optionally interrupted by one ormore oxygen atoms, B₂ is C₁ -C₆ -alkylene and X signifies halogen, andoptionally one or more further copolymerisable monomers, in the absenceor presence of an additional vinylic comonomer.
 2. Ophthalmic mouldingaccording to claim 1, which is a contact lens.
 3. Ophthalmic mouldingaccording to claim 1, characterised in that it is obtained bycrosslinking a prepolymer, which is the copolymerisation product of thecomponents (a), (b), (c) and (d) given in claim 1, in the absence orpresence of an additional vinylic comonomer.
 4. Ophthalmic mouldingaccording to claim 1, wherein R₂ is linear or branched C₆ -C₁₀-alkylene, cyclohexylene-methylene orcyclohexylene-methylene-cyclohexylene which are either unsubstituted orsubstituted in the cyclohexyl moiety by 1 to 3 methyl groups, orphenylene or phenylene-methylene-phenylene which are eitherunsubstituted or substituted in the phenyl moiety by methyl. 5.Ophthalmic moulding according to claim 1, obtained by crosslinking aprepolymer, which is the copolymerisation product of(a) one or morepolyalkylene glycols of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --H(1 a),

wherein one of radicals Y₁ and Y₂ signifies methyl and the other radicalsignifies hydrogen, and n and m, independently of one another, eachdenote a number from 0 to 50, wherein the sum of (n+m) is 8 to 50, (b)(i) one or more polyhydroxy compounds of formula

    R.sub.1 --(OH).sub.x                                       ( 2)

wherein R₁ is the radical of a multi-functional aliphatic alcohol and xis a number from 3 to 8, (c) one or more diisocyanates of formula

    OCN--R.sub.2 --NCO                                         (3a),

wherein R₂ signifies linear or branched C₃ -C₈ -alkylene orunsubstituted or C₁ -C₄ -alkyl-substituted or C₁ -C₄ -alkoxy-substitutedC₆ -C₁₀ -arylene, C₇ -C₁₈ -aralkylene, C₆ -C₁₀ -arylene-C₁ -C₂-alkylene-C₆ -C₁₀ -arylene, C₃ -C₈ -cycloalkylene, C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene, C₃ -C₈ -cycloalkylene-C₁ -C₂-alkylene-C₃ -C₈ -cycloalkylene or C₁ -C₆ -alkylene-C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene, and (d) one or more ethylenicallyunsaturated compounds of formula ##STR10## wherein R₃ is hydrogen ormethyl, B₁ signifies linear or branched C₂ -C₈ -alkylene, B₂ is C₁ -C₄-alkylene, z1 signifies the number 0 or 1 and X represents halogen, inthe absence or presence of an additional vinylic comonomer in a mould.6. Ophthalmic moulding according to claim 1, obtained by crosslinking aprepolymer, which is the copolymerisation product of(a) one or morepolyalkylene glycols of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --H(1a),

wherein one of radicals Y₁ and Y₂ signifies methyl and the other radicalsignifies hydrogen, and n and m, independently of one another, eachdenote a number from 0 to 25, wherein the sum of (n+m) is 9 to 25, (b)one or more polyhydroxy compounds selected from the group consisiting ofglycerol, diglycerol, triglycerol, 1,1,1-trishydroxymethylethane,1,1,1-trishydroxymethylpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol,erythritol, pentaerythritol, di- or tripentaerythritol, arabitol,sorbitol, disorbitol and mannitol and mixtures thereof, (c) adiisocyanate of formula

    OCN--R.sub.2 --NCO                                         (3a),

wherein R2 signifies linear or branched C₆ -C₁₀ -alkylene,cyclohexylene-methylene or cyclohexylene-methylene-cyclohexylene eitherunsubstituted or substituted in the cyclohexyl moiety by 1 to 3 methylgroups, or phenylene or phenylene-methylene-phenylene eitherunsubstituted or substituted in the phenyl moiety by methyl, and (d) anethylenically unsaturated monoisocyanate of formula ##STR11## wherein R₃denotes hydrogen or methyl and B₁ signifies linear C₂ -C₄ -alkylene, inthe absence or presence of an additional vinylic comonomer in a mould.7. Prepolymer which is the copolymerisation product of components (a),(b), (c) and (d) given in claim
 1. 8. Prepolymer according to claim 7,which is the copolymerisation product of(a) one or more polyalkyleneglycols of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --H(1 a),

wherein one of radicals Y₁ and Y₂ signifies methyl and the other radicalsignifies hydrogen, and n and m, independently of one another, eachdenote a number from 0 to 50, wherein the sum of (n+m) is 8 to 50, (b)(i) one or more polyhydroxy compounds of formula

    R.sub.1 --(OH).sub.x                                       ( 2)

wherein R₁ is the radical of a multi-functional aliphatic orcycloaliphatic alcohol and x is a number from 3 to 8, (c) one or morediisocyanates of formula

    OCN--R.sub.2 --NCO                                         (3a),

wherein R₂ signifies linear or branched C₃ -C₁₈ -alkylene orunsubstituted or C₁ -C₄ -alkyl-substituted or C₁ -C₄ -alkoxy-substitutedC₆ -C₁₀ -arylene, C₇ -C₁₈ -aralkylene, C₆ -C₁₀ -arylene-C₁ -C₂-alkylene-C₆ -C₁₀ -arylene, C₃ -C₈ -cycloalkylene, C₃ -C₈-cycloalkylene-C₁ -C₆ -alkylene, C₃ -C8-cycloalkylene-C₁ -C₂-alkylene-C₃ -C₈ -cycloalkylene or C₁ -C₆ -alkylene-C₃-C8-cycloalkylene-C₁ -C₆ -alkylene, and (d) one or more ethylenicallyunsaturated compounds of formula ##STR12## wherein R₃ is hydrogen ormethyl, B₁ signifies linear or branched C₂ -C₈ -alkylene, B₂ is C₁ -C₄ -alkylene, z1 signifies the number 0 or 1 and X represents halogen. 9.Prepolymer according to claim 7, which is the copolymerisation productof(a) one or more polyalkylene glycols of formula

    HO--(CH.sub.2 --CH.sub.2 --O).sub.n --(CHY.sub.1 --CHY.sub.2 --O).sub.m --H(1 a),

wherein one of radicals Y₁ and Y₂ signifies methyl and the other radicalsignifies hydrogen, and n and m, independently of one another, eachdenote a number from 0 to 25, wherein the sum of (n+m) is 9 to 25, (b)one or more polyhydroxy compounds selected from the group glycerol,diglycerol, triglycerol, 1,1,1-trishydroxymethylethane,1,1,1-trishydroxymethylpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol,erythritol, pentaerythritol, di- or tripentaerythritol, arabitol,sorbitol, disorbitol and mannitol or mixtures thereof, (c) adiisocyanate of formula

    OCN--R.sub.2 --NCO                                         (3a),

wherein R₂ signifies linear or branched C₆ -C₁₀ -alkylene,cyclohexylene-methylene or cyclohexylene-methylene-cyclohexylene eitherunsubstituted or substituted in the cyclohexyl moiety by 1 to 3 methylgroups, or phenylene or phenylene-methylene-phenylene eitherunsubstituted or substituted in the phenyl moiety by methyl, and (d) anethylenically unsaturated monoisocyanate of formula ##STR13## wherein R₃denotes hydrogen or methyl and B₁ signifies linear or branched C₂ -C₄-alkylene.
 10. Process for the production of a prepolymer according toclaim 7, wherein components (a), (b), (c) and (d) given in claim 1 arereacted together, in any sequence, in an inert solvent at a temperatureof -5° C. to 150° C.
 11. Process according to claim 10, wherein amixture of components (a) and (b) is either reacted with a mixture ofcomponents (c) and (d) or firstly with component (c) and then withcomponent (d).
 12. Process according to claim 10, wherein a mixture of 1OH equivalent of component (a) and 0.05 to 1 OH equivalents of component(b) is reacted in an inert solvent at a temperature of 0 to 100° C. inthe presence of a catalyst either with a mixture of 0.5 to 1.95 NCOequivalents of a component (c) and 0.1 to 2 NCO or acid halideequivalents of a component (d) or first of all with 0.5 to 1.95 NCOequivalents of a component (c) and then with 0.1 to 2 NCO or acid halideequivalents of a component (d).
 13. Process according to claim 10,wherein a mixture of 1 OH equivalent of component (a) and 0.1 to 0.8 OHequivalents of component (b) is reacted, in an inert solvent at atemperature of 0 to 80° C., in the presence of a catalyst selected fromthe group of metal salts of organic carboxylic acids and tertiary amine,first of all with 0.6 to 1.5 NCO equivalents of component (c) and thenwith 0.1 to 1.5 NCO or acid halide equivalents of a component (d). 14.Process for the production of a moulding, wherein it comprises thefollowing steps:a) introducing a prepolymer, which is obtained accordingto one of claims 7 to 13 and is liquid or readily meltable at roomtemperature, and which is essentially free from solvents, into a mould,in the absence or presence of an additional vinylic comonomer, andsupplementing with a photo-initiator, b) initiating thephoto-crosslinking by exposure to actinic radiation, c) opening themould, so that the moulded article can be removed from the mould. 15.Process according to claim 14, wherein the process is carried out in theabsence of an additional vinylic comonomer.
 16. Process for theproduction of a moulding, wherein it comprises the following steps:a)producing a water-soluble prepolymer, which is obtained according to oneof claims 7 to 13, in an essentially aqueous solution, in the absence orpresence of an additional vinylic comonomer, and supplementing with aphoto-initiator, b) introducing the solution obtained into a mould, c)initiating the photo-crosslinking by exposure to actinic radiation, d)opening the mould, so that the moulded article can be removed from themould.
 17. Process according to claim 16, whrein the process is carriedout in the absence of an additional vinylic comonomer.